Vehicle emission control systems may be configured to store fuel vapors from fuel tank refueling and diurnal engine operations in a fuel vapor canister, and then purge the stored vapors during a subsequent engine operation. The stored vapors may be routed to engine intake for combustion, further improving fuel economy.
In a typical canister purge operation, a canister purge valve coupled between the engine intake and the fuel canister is opened, allowing for intake manifold vacuum to be applied to the fuel canister. Simultaneously, a canister vent valve coupled between the fuel canister and atmosphere is opened, allowing for fresh air to enter the canister. This configuration facilitates desorption of stored fuel vapors from the adsorbent material in the canister, regenerating the adsorbent material for further fuel vapor adsorption.
However, engine run time in PHEVs may be limited, and thus opportunities for purging fuel vapor from the canister may also be limited. If the PHEV is parked in a location with a high ambient temperature (and/or direct sunlight, hot parking surface, etc.) while the fuel vapor canister is saturated with fuel vapors, fuel vapor may desorb from the canister and escape to atmosphere. For example, this scenario may occur following a refueling event, if the PHEV is driven subsequently driven in electric-only mode and parked. This could result in the vehicle failing emissions testing, and potentially losing classification as a practically zero emissions vehicle (PZEV).
The inventors herein have recognized the above problems, and have developed systems and methods to at least partially address these problems. In one example, a method for a plug-in hybrid electric vehicle, comprising: during a first condition, including an engine-off condition and the plug-in hybrid electric vehicle coupled to an external power source, cooling a vapor canister based on an ambient temperature. In this way, bleed emissions may be reduced in PHEVs during conditions when the vehicle is parked and recharging at a high ambient temperature.
In another example, a system for a plug-in hybrid electric vehicle, comprising: a fuel vapor canister coupled to a fuel tank via a fuel tank isolation valve and further coupled to an engine intake via a purge valve; a temperature sensor coupled to the fuel vapor canister; and a control system including executable instructions stored in non-transitory memory for adjusting cooling of the fuel vapor canister based on a desired canister temperature. In this way, the canister adsorbence may be increased either prior to or following a refueling event, thus decreasing evaporative emissions.
In yet another example, a method for a plug-in hybrid electric vehicle, comprising: during a first condition, including an engine-off condition, the plug-in hybrid electric vehicle coupled to an external power source, a fuel vapor canister load above a threshold, a fuel tank vacuum below a threshold, and an ambient temperature above a threshold, cooling a fuel vapor canister using power from the external power source. In this way, power from the external power source may be used to cool the fuel vapor canister, thereby decreasing bleed emissions without expending battery energy.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.